A Symptomatic Pelvic Rib M

A symptomatic pelvic rib M. Podgórski1, D. Gwizdała1, P. Flont2, K. Niedzielski2, M. Polguj3, P. Grzelak4

1Department of Radiology and Imagining Diagnostic, Polish Mother’s Memorial Hospital Research Institute, Lodz, Poland 2Department of Orthopedics and Traumatology, Polish Mother’s Memorial Hospital Research Institute, Lodz, Poland 3Department of Angiology, Medical University of Lodz, Poland 4Department of Radiology and Diagnostic Imaging, Medical University of Lodz, Poland

[Received: 8 February 2017; Accepted: 12 June 2017]

Pelvic rib is a rare anomaly where ectopic rib is found in a pelvic region. It is usually found occasionally in asymptomatic patients. We report a case of 15-year-old male, diagnosed with a symptomatic pelvic rib. It had an unusual presentation creating a pseudotumour associated with pain and reduced range of motion in the hip joint. Patient was operated on with good result and final diagnosis was confirmed in pathological examination. (Folia Morphol 2018; 77, 2: 406–408)

Key words: congenital anomaly, accessory rib, pelvic digit, ischium, eleventh finger

INTRODUCTION to admission symptoms rapidly aggravated, limit- The pelvic rib (pelvic digit) is a rib-like bony struc- ing mobility with need for crutches, also reducing ture that may arise from bones of the pelvis. It is the range of motion in right hip joint. Patient had considered to be a congenital abnormality of the de- no medical history of trauma or musculoskeletal veloping bone in close proximity to a bony pelvis [3]. abnormalities. Initially, the X-ray of the right hip It can consist from a few segments creating pseu- showed no abnormalities. On pelvic MRI compres- doarticulations (also with surrounding bones). Pelvic sion of roots of the spinal cord was ruled out. Pa- rib usually causes no symptoms and is incidentally tient was admitted to Department of Orthopaedics found on radiograms; however, it should be differ- and Traumatology. Physical examination revealed entiate from other pathologies like osteochondroma a palpable tumour, located medially to the right or dysontogenetic tumours [6, 10]. ischial tuberosity (on the border of buttock and In this report we present a management of upper thigh) with pain upon compression. Slightly a 15-year-old male who was operated on for a symp- positive Lasegue’s sign was present. Basic labora- tomatic pelvic rib that arose from an ischium. During tory tests (complete blood count, ESR, CRP) were the surgery, data from conventional X-ray, computed within normal limits. Pelvis X-ray revealed an acces- tomography (CT) and magnetic resonance imaging sory, well calcified linear structure projected over (MRI) were applied. the ischium (Fig. 1A). Diagnosis was completed by a non-contrast CT scan confirming the presence of CASE REPORT inhomogeneous area in the medial group of the The 15-year-old, male presented with a 2-year thigh muscles, with a longitudinal bony structure history of progressive pain in the right gluteal area, and smaller band-like calcifications (Fig. 1B). The radiating to the posterior part of the thigh and to remaining bone structures in the pelvis and right the calf. Symptoms occurred periodically, initially thigh did not show any pathological changes. Due following jumping exercise. Six to eight weeks prior to unusual character of the soft tissues surround-

Address for correspondence: M. Podgórski, MD, PhD, Department of Radiology and Imagining Diagnostic, Polish Mother’s Memorial Hospital Research Institute, ul. Rzgowska 281/289, 93–338 Łódź, Poland, tel: +48 42 27 11 571, e-mail: [email protected]

406 M. Podgórski et al., A symptomatic pelvic rib

A B

C D

Figure 1. A. Antero-posterior pelvic X-ray with the limbs adducted. The pelvic rib (arrow) presents as a bony structure between the right ischium and lesser trochanter of the right femur. Despite the positioning asymmetry remaining bones appear normally; B. Three-dimensional volume rendering (VR) multi-detector computed tomography showing the pelvic rib (arrow), size 60 × 20 × 10 mm articulating with the ischium; C. Magnetic resonance imaging in transverse T1W sequences. Well defined, intramuscular mass (arrow) with a size of 71 × 60 × 56 mm and non-uniform signal intensity (containing elements of haemoglobin degradation) compressing surrounding structures; D. Removal of the pelvic rib (held with pean).

ing the bone protuberance a two phase MRI was the patient was discharged with no deficiency in performed which revealed a well isolated mass range of motion. (71 × 60 × 56 mm) located between head, neck, and lesser trochanter of right femur and ischium, DISCUSSION which had a signal equivalent to a haematoma. The majority of additional ribs are connected to The mass was located intramuscularly, compress- transitional vertebrae of the cervical or lumbar spine [2]. ing surrounding tissues and dislocating adjacent Their occurrence in the pelvis is unusual. Ectopic ribs muscle groups. In its posterior part there was usually arise from the ilium, sacrum and coccyx [3–5]; a longitudinal, bone-like structure (60 × 15 mm). however, an association with the ischium, like in our The lateral part of this mass had a typical structure case, is very rare. To the best of our knowledge, only of the long bone including cortical bone (Fig. 1C). Granieri and Bacarini [4] and Greenspan and Nor- The sciatic nerve was situated 10 mm dorsally of man [5] describe 3 patients with a similar lesion the tumour. The femoral artery, vein and nerve adjacent to the ischium. Pelvic ribs can develop as were located 35 mm in front of the described mass. a single, longitudinal, well calcified structure, with There was no lymphadenopathy. Due to increas- a proper differentiation of cortex and medulla and ing pain limiting physical activity and the need may consist of a few segments creating false joints, to exclude malignancy the patient was qualified also with bony pelvis [7]. for surgery. The bony mass, macroscopically re- Occurrence of pelvic rib seems to result from the sembling a small rib (6 cm in length and cross- migration of embryonic mesoderm, with ability to section of 2 × 1 cm) and a surrounding hematoma form a rib, into the pelvic region [1]. Other authors were removed (Fig. 1D). Histopathology showed suggest that this mass is formed during mesenchymal a typical bone structure. Fifteen days after surgery bone growth that occurs before the sixth week of

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